What name is given to those isotopes which have unstable nuclei and emit various types of radiations?

What is the relationship between an atom containing 11 protons, 11 electrons ad 11 neutrons, and another atom containing 11 protons, 11 electrons and 12 neurtrons?

What name is given to the pair of atoms such as?

Fill in the following blanks in respect of an atom of an element:

Complete the following statements:

(a) Magnesium has 3 valence electrons in the ………… shell.

(b) The valency of nitrogen in N₂ molecule is ……….

(c) Isotopes have different mass numbers because their nuclei contain different number of ……….

(d) Some boron atoms have mass number 10 and some have mass number 11. These boron atoms with different mass number are called ……...